The present invention relates to electrical receptacles of the type having slidable shutter mechanisms arranged behind the openings which receive the blades or prongs of an electrical plug connected to the receptacle. More specifically, the invention relates to receptacles of this type which are adapted to receive either a plug having two parallel prongs, or a plug having tandem or orthagonally disposed prongs.
In order to prevent electrical shocks and possible injuries which could result from insertion of an electrically conducting member into the live terminals of an electrical receptacle, shutter mechanisms have been provided as a safety feature. One type of such shutter mechanism and associated receptacle is shown in U.S. Pat. No. 4,379,607 of the present inventor which is designed to accept a conventional plug of the type having parallel prongs with flat sides lying in substantially parallel planes. Such plugs are generally associated with devices requiring 15 ampere operation, and are thus commonly referred to as 15 amp parallel blade plugs.
Another type of conventional plug has prongs or blades which extend along parallel axes, but which have flat sides arranged in perpendicular (orthogonal, or tandem) planes. These plugs are generally used in connection with 20 ampere operation, thus being commonly termed 20 amp tandem blade plugs. Standard forms of receptacles are provided which will accept both types of plugs, one of the prong-receiving slots being elongated in a first direction and the other slot being T-shaped, having a first portion elongated in a direction parallel to the first slot and a second portion extending at 90 degrees from the mid-point of the first portion, whereby the second portion of the second slot is elongated in a direction perpendicular to the first slot.
A shutter mechanism for a receptacle adapted to receive both of the aforementioned types of plugs is shown in U.S. Pat. No. 4,544,219, issued Oct. 1, 1985, of Barkas. This shutter mechanism includes two slidable shutter members, one of which includes a portion arranged under the T-shaped slot which is divided to form a gap under the portion of the slot which receives the tandem blade. Upon full insertion of such blade, the portions of the shutter member on opposite sides of the gap are forced apart to permit the end of the blade to enter the terminals of the receptacle. Since a relatively small, molded, plastic part must be flexed at two points each time a tandem blade plug is inserted into and withdrawn from the receptacle, and since a misaligned insertion of such a plug may result in a greater amount of flexure than that intended, there is the danger of breakage of the shutter mechanism, requiring replacement of the entire receptacle.
The general object of the present invention is to provide a novel and improved shutter mechanism for an electrical receptacle adapted to receive both parallel and tandem blade plugs.
A more specific object is to provide a shutter mechanism for an electrical receptacle which will receive a tandem blade plug without requiring flexure of any parts of the shutter mechanism.
Other objects will in part be obvious and will in part appear hereinafter.